Allogeneic stem cell transplantation from HLA identical donor in high-risk sarcoma

9561 Background: To evaluate the feasibility of an allogeneic stem cell transplantation (ASCT) from HLA identical donor in patients (pts) affected by resistant or relapsed rabdhomyosarcoma (RMS) or Ewing sarcoma (ES) in which the 1 year probability of survival is lesser than 5%. Methods: 21 pts, median age 16 (6-22) years, affected by resistant (3) or relapsed (8) RMS and resistant (6) or relapsed (4) ES, were enrolled and submitted to an ASCT after a conditioning regimen consisting of thiotepa + melphalan ± fludarabine or cyclophosphamide. The donor was an identical sibling in 14 cases or an unrelated donor (UD) in 7. At time of transplant 19 pts were in PR and 2 (1 RMS and 1 ES) in progressive disease. Graft versus host disease (GVHD) prophylaxis consisting of cyclosporin A ± anti-lymphocytic serum and short term methotrexate in UD setting. SC sources were bone marrow in 13 cases and peripheral blood in 8. Results: The reconstitution of bone marrow function was obtained in all the 21 pts. Acute GVHD of grade II-IV occurred in 6 pts and a complete marrow donor chimerism was observed after 40 and 60 days in sibling and UD setting respectively. After a median follow-up of 28 (1-58) months for ES and 4 (1-18) months for RMS, 8 pts (5 RMS and 3 ES) relapsed, 14 dead (7 for progressive disease and 7 for TRM) and 6 pts are alive and well. The 1 years probability of OS (SE) and EFS (SE) were 0.43 (0.19) and 0.29 (0.17) for ES and 0.37 (0.16) and 0.14 (0.12) for RMS. The 100 days probability of TRM was 0.00 for ES and 0.29 (0.14) for RMS. Conclusions: Despite an high TRM in RMS pts, our experience shows the feasibility of an allogeneic ASCT in relapsed or resistant sarcomas even in heavily pre treated pts. On the basis of these observations a prospective national study is now open on behalf of Associazione Italiana di Ematologia ed Oncologia Pediatrica (AIEOP), Gruppo Italiano Trapianto Midollo Osseo (GITMO) and Italian Sarcoma Group (ISG), to evaluate the efficacy of a reduced intensity conditioning regimen followed by ASCT from related or unrelated HLA identical donor for poor prognosis at diagnosis SE and RMS in paediatric and adult pts. No significant financial relationships to disclose.